Optical transmitting apparatus

An optical transmitting apparatus comprising:

• a modulating unit that branches an input light and performs independent phase modulation to branched optical signals of arms;
• a phase adjusting unit that changes a phase difference between the optical signals of respective arms according to a control signal;
• a combining unit that combines modulated lights having the phase difference;
• an acquiring unit that acquires a positive-phase signal and a negative-phase signal from the combining unit;
• a multiplying unit that obtains a product of the positive-phase signal and the negative-phase signal acquired by the acquiring unit;
• a detecting unit detecting a power of a product signal from multiplication by the multiplying unit;
• and
• a control unit that changes the control signal according to signal component intensity detected by the detecting unit.

A control method of an optical transmitting apparatus comprising:

• branching an input light and performing independent phase modulation to branched optical signals of arms;
• changing a phase difference between the optical signals of respective arms according to a control signal;
• combining modulated lights having the phase difference;
• acquiring a positive-phase signal and a negative-phase signal;
• obtaining a difference between the positive-phase signal and the negative-phase signal;
• detecting a power of a differential signal from subtraction;
• and
• changing the control signal according to signal component power detected by the detecting unit.